# False positive elevation in serum creatinine: a case report

## TL;DR

A 68-year-old woman had falsely elevated creatinine levels due to a paraprotein, highlighting the need to consider this in patients without other kidney disease signs.

## Contribution

The case highlights paraprotein-induced false creatinine elevation and emphasizes the importance of clinical-laboratory communication.

## Key findings

- Elevated creatinine levels were confirmed as false through radioisotope GFR and cystatin C.
- No kidney damage was found despite high creatinine, indicating paraprotein interference.
- Diluting the sample reduced creatinine levels, supporting the false elevation hypothesis.

## Abstract

Paraproteins can interfere with several substances, producing erroneous laboratory measurements. The diagnosis of kidney disease in patients with hematological disorders has important prognosis implications. An elevated creatinine with no other signs of kidney disease should prompt the idea of a spurious creatinine. Communication between the clinical team and the laboratory is key.

In this case, we present a 68-year-old woman with an elevated creatinine and an IgM lambda paraprotein. Interestingly, there were no other signs of chronic kidney disease besides the creatinine value, with no albuminuria or microhematuria. A kidney biopsy showed normal parenchyma and ruled out the possibility of paraprotein-related damage. The monoclonal component and creatinine levels raised parallelly during follow-up while maintaining normal urea levels. This prompted the hypothesis of a falsely elevated creatinine. It was confirmed with a normal glomerular filtration rate determined by a radioisotope, a cystatin C measurement and a reduction in creatinine when diluting the sample.

It is important to consider the possibility of a falsely elevated creatinine in patients with paraproteinemia and no other signs of kidney disease to avoid unnecessary diagnostic tests and for the prognostic implications.